1. Field of the Invention
The present invention relates to an engine flywheel.
2. Description of the Related Art
An engine flywheel is mounted on the crankshaft of an engine, and functions as an inertial mass for reducing rotational variation in an engine. Conventionally, a simple circular plate, or in other words, a plain type flywheel, has generally been used as this type of flywheel.
However, when the present inventors coupled a plain type flywheel and an automatic transmission (AT) torque converter in a V6 engine and conducted tests on the engine during idling, a problem occurred in that a knocking sound was generated.
More specifically, as is illustrated in FIG. 12, when the engine is driven, the crank system 55, comprising a crankshaft 51, flywheel 52, flexplate 53 and torque converter 54, rotates, generating bending vibration B which results in axial vibration L. At this time, the crank arm 56 and the like vibrate in an axial direction (thrust direction), colliding with the bearing 58 on the cylinder block side which supports the crank journal 57. The knocking sound is generated upon this collision, and becomes very unpleasant to the ear.
In more detail, as is illustrated in FIG. 13, bearing metal 59 and thrust metal 60 are integrally fixed to the bearing 58. The crank journal 57 is supported by the bearing metal 59 so as to be free to rotate, and the crank arm 56 is supported in the thrust direction by the thrust metal 60. There is a small gap between the crank arm 56 and the thrust metal 60, and accompanying the axial vibration of the crank system, the crank arm 56 vibrates within the range of this gap, thereby banging against the thrust metal 60 and generating a knocking sound.
In order to prevent this knocking sound, the bending vibration B and the resultant axial vibration L must be suppressed. To this end, a flywheel which is spoked to reduce the weight of the flywheel has been devised.
However, “spoked” has various formations, and not only can the utmost effects not be obtained by simply making the flywheel spoked, but conversely, the knocking sound may even be aggravated thereby.